Arsenic Ylids

Stibonium Ylids and Related Compounds. In contrast to phosphoms and arsenic, only a few antimony yhds have been prepared. Until quite recendy triphenyl stibonium tetraphenylcyclopentadienyUde [15081 -36-4] C H Sb, was the only antimony yUd that had been isolated and adequately characteri2ed (192). A new method, uti1i2ing an organic copper compound as a catalyst, has resulted ia the synthesis of a number of new antimony yhds (193) ... 

Cleavage reactions are best carried out in aqueous solution. In aprotic solvents, electrogenerated bases lead to the conversion of onium salts to the ylids which are not reducible [49]. The sequence of reactions shown in Scheme 5.2 shows that the bond cleavage process for phosphonium salts proceeds with retention of configuration around the phosphorus atom [50]. Retention of configuration at arsenic is also observed [51]. This electrochemical process is a route to asymmetric trisub-stituted phosphorus and arsenic centres. 

A123. A. W. Johnson, Ylid Chemistry. Academic Press, New York, 1966. This book is mainly about organophosphorus compounds, but there is one chapter of 20 pp. (39) on arsenic and antimony ylids. 

Following this initial preparation of a stable material having an ylid structure, a variety of phosphorus, arsenic, and sulfur ylids have been prepared and characterized and their chemistry has been thoroughly reviewed 78>. The chemistry of trimethylamine imine 2> and trimethyl-amine oxide, compounds which are isoelectronic with the ylid, have been reviewed 30,78) and will not be described here. 

Ylids of arsenic have been obtained by elimination of hydrogen halides from arsonium compounds 211). 

Fluorophosphoranes can be obtained from phosphonous and phosphinous halides by reactions with arsenic or antimony obtained with KHF2 (6.518). Some phosphinous halides react with sulphur compounds to give phosphinothioites (9.420), with phenyl azide to give monophosphazenes (7.447), and with ylids fluorides (6.504, 6.505). Hydrofluorophosphoranes produces phosphonium salts (6.377). Phosphonous and phosphinous halides can be condensed to form polyphosphines or cyclic derivatives (6.660, 6.666,6.680,6.684), or reacted to give P-P linkages (6.737). 

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